Certain Employee Benefit and Stock-Based Compensation Plans (Summary of Components of Net Periodic Benefit Cost) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Qualified Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 25	$ 21	$ 51	$ 47
Interest cost	48	49	96	98
Expected return on plan assets	(71)	(74)	(142)	(149)
Amortization of prior service cost	(2)	(2)	(4)	(3)
Amortization of actuarial losses	22	5	44	9
Net periodic cost (benefit)	22	(1)	45	2
Nonqualified Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	1	1	2	2
Interest cost	4	4	7	7
Amortization of actuarial losses	1	1	3	2
Net periodic cost (benefit)	6	6	12	11
Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	2	3	3	4
Interest cost	4	4	8	9
Expected return on plan assets				(1)
Amortization of prior service cost	(1)	(1)	(2)
Amortization of actuarial losses	(1)
Net periodic cost (benefit)	$ 4	$ 6	$ 9	$ 12